Field of the Invention
The present invention relates to a liquid crystal display device having a touch sensing function and a color filter used for the same.
Discussion of the Background
In a touch sensing operation in which a location of a pointer or an operation is detected, on-cell type touch panels have been widely used for liquid crystal display devices. On-cell type touch panels are provided on each liquid crystal cells. Types of touch panel include an electrostatic capacitance type, resistive film type, optical type, electromagnetic induction type or the like. In recent years, electrostatic capacitance type has been widely used because of the ease of handling. For example, patent literature 1 (Japanese Patent Application Laid-Open Publication Number 1993-324203) discloses an electrostatic capacitance type touch panel.
In a case where an on-cell type touch panel is provided in portable equipment or the like, thickness and weight of the portable equipment increases. Hence, provision of on-cell type touch panels is sometimes avoided in portable equipment.
A technique for forming a transparent conductive film on the front surface of a transparent glass substrate and forming a shield electrode on the back surface of the substrate is disclosed, for example, by patent literature 1 (Japanese Patent Application Laid-Open Publication Number 1993-324203). As a similar technique, patent literature 2 (Japanese Patent Application Laid-Open Publication Number 2008-185785) discloses a technique that detects electrostatic capacitance by using a dielectric such as a polarizing plate formed on a detection electrode which is formed on the front surface (outer surface) of the second substrate which is provided with a color filter. In patent literature 2, a shield conductor is further provided on a side that comes into contact with the liquid crystal layer. However, the patent literatures 1 and 2 do not disclose a position detecting technique in which a transparent electrode pattern of X-direction and a transparent electrode pattern in the Y-direction are formed on a transparent substrate such as a glass substrate and high-precision touch sensing by a pointer is accomplished. Further, patent literatures 1 and 2 disclose a configuration having a shield electrode to detect a capacitive component.
Patent literature 3 (international publication number WO 2007/102238) discloses a configuration in which a shield electrode is provided and electrodes related to a touch sensing are disposed in the liquid crystal cell. However, patent literature 3 does not disclose a technique that enhances detection accuracy of electro capacitive type touch sensing.
Patent literature 4 (Japanese Patent Application Laid-Open Publication Number 2010-160745) discloses a color filter using a conductive light shielding portion, capable of being disposed in a liquid crystal cell and of being applied to electrostatic capacitive type touch sensing. However, patent literature 4 does not disclose a technique that enhances detection accuracy of electro capacitive type touch sensing.
Patent literature 5 (Japanese Patent Application Laid-Open Publication Number 2012-93649) discloses a color filter substrate used for a fringe field switching mode liquid crystal display device. According to the color filter of the patent literature 5, red pixels, green pixels and blue pixels are separated by a black matrix. In the embodiment of the patent literature 5, the black matrix is formed by using a black coloring composition with a thickness of 2 μm. A configuration in which colored pixels are formed on a black material having a large film thickness is not supposed to be used for high precision pixels for portable display device having, for example, 400 ppi (pixels per inch). In a case where a protrusion of the colored layer which is formed when the colored layer is coated on the black matrix having a thickness of 2 μm and a variation of a film thickness of the colored pixels become large, liquid crystal alignment fluctuates so that it is hard to perform liquid crystal display in an uniform manner. Moreover, in patent literature 5, no touch sensing technique is disclosed and influences on the liquid crystal molecules and the liquid crystal alignment caused by high electrostatic discharge propagated from the electrode that detects electrostatic capacitance during a touch operation are not considered.
According to paragraph [0105] and FIG. 34 of patent literature 6 (Japanese Patent Application Laid-Open Publication Number 2009-199093), a configuration is disclosed in which two ITO (indium-tin-oxide) layers related to touch sensing as a concept B are formed on both surfaces of the upper glass, and a color filter and Vcom (ITO3) on the color filter are provided.